I know this sounds nuts and not so sure I want to admit this, BUT...I wiggle the lid after I close it. I left one lid slightly lifted and after having spent some serious cash on my frogs I freaked out that I may have lost one. So now I wiggle the lid after I close it to make sure it has sit right on the top of the tank. Then after I turn the lights off in the room I may do it again. See, now I feel like I have a small OCK tick or somthing...